PHIVEBSITY  OF   CALIFORNIA   PPBLICATIOH8 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


SOME  FACTORS  AFFECTING  THE  QUALITY 

OF  RIPE  OLIVES  STERILIZED  AT 

HIGH  TEMPERATURES 


BY 

W.  V.  CRlfESS 


BULLETIN  No.  333 

October,  1921 


UNIVERSITY  OF  CALIFORNIA  PRESS 

BERKELEY 

1921 


David  P.  Barrows,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 

HEADS   OF  DIVISIONS 

Thomas  Forsyth  Hunt,  Dean. 

Edward  J.  Wickson,  Horticulture  (Emeritus). 

,  Director  of  Resident  Instruction. 

C.  M.  Haring,  Veterinary  Science,  Director  of  Agricultural  Experiment  Station. 

B.  H.  Crocheron,  Director  of  Agricultural  Extension. 
Hubert  E.  Van  Norman,  Dairy  Management. 

James    T.   Barrett,    Plant   Pathology;    Acting   Director    of    Citrus    Experiment 

Station 
William  A.  Setchell,  Botany. 
Myer  E.  Jaffa,  Nutrition. 
Ralph  E.  Smith,  Plant  Pathology. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 

John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Fruit  Products. 
Warren  T.  Clarke,  Agricultural  Extension. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
Walter  Mulford,  Forestry. 
Fritz  W.  Woll,  Animal  Nutrition. 
W.  P.  Kelley,  Agricultural  Chemistry.  - 
H.  J.  Quayle,  Entomology. 
Elwood  Mead,  Rural  Institutions. 
H.  S.  Reed,  Plant  Physiology. 
L.  D.  Batchelor,  Orchard  Management. 
J.  C.  Whitten,  Pomology. 
fFRANK  Adams,  Irrigation  Investigations. 

C.  L.  Roadhouse,  Dairy  Industry. 
R.  L.  Adams,  Farm  Management. 

W.  B.  Herms,  Entomology  and  Parasitology. 

F.  L.  Griffin,  Agricultural  Education. 
John  E.  Dougherty,  Poultry  Husbandry. 

D.  R.  Hoagland,  Plant  Nutrition. 

G.  H.  Hart,  Agricultural  Engineering. 

L.  J.  Fletcher,  Agricultural  Engineering. 
Edwin  C.  Voorhies,  Assistant  to  the  Dean. 

division  of  viticulture  and  fruit  products 

Frederic  T.  Bioletti  W.  V.  Cruess 

L.  O.  Bonnett  A.  W.  Christie 

G.  Barovetto  J.  H.  Irish 


t  In  cooperation   with   Office  of  Public  Roads   and  Rural  Engineering,   U.   S. 
Department  of  Agriculture. 


SOME   FACTORS   AFFECTING   THE   QUALITY 

OF   RIPE   OLIVES   STERILIZED   AT 

HIGH   TEMPERATURES 


By  W.  V.  CRUESS 


CONTENTS 

PAGE 

1.  Introduction 221 

2.  Variety    .". 222 

3.  Maturity    222 

4.  Holding  Solution  222 

5.  Lye  Treatment  223 

6.  Bacterial  Action  224 

7.  Salt  Concentration  used  in  Canning 225 

8.  Increase  of  Acidity  of  Brine 226 

9.  Temperature  226 

10.  Character  of  Container 229 

11.  Summary  and  Conclusions 231 

The  California  State  Board  of  Health,  ruled  in  August,  1920,  that 
pickled  ripe  olives  which  are  to  be  offered  for  sale  must  be  sterilized 
at  240°  F.  for  40  minutes  in  steam  pressure  retorts  equipped  with 
accurate  recording  thermometers.  This  regulation  was  based  on  the 
results  of  investigations  upon  the  death  temperature  of  Bacillus  botu- 
linus  conducted  by  Dr.  E.  C.  Dickson,  of  the  Stanford  University 
Medical  School,  and  Dr.  K.  F.  Meyer,  of  the  University  of  California. 

During  the  season  of  1919  experiments  by  the  writer  demonstrated 
that  sterilization  of  olives  at  240°  F.  to  250°  F.  resulted  in  many  cases 
in  softening  and  in  severe  injury  to  the  flavor,  and  at  the  beginning 
of  the  1920-21  olive  canning  season,  when  the  regulation  of  the  State 
Board  of  Health  was  for  the  first  time  put  into  general  effect,  it  was 
found  that  much  of  the  fruit  softened  and  acquired  a  disagreeable 
'  '  scorched ' '  flavor.  In  some  instances  both  defects  developed,  in  others 
only  the  scorched  flavor.  Olives  from  different  factories  and  from 
different  pickling  vats  in  the  same  factory  varied  greatly  in  their 
behavior. 

The  investigations  reported  in  this  bulletin  were  undertaken  in  an 
attempt  to  determine  the  causes  of  the  observed  differences,  and  have 
extended  over  two  canning  seasons. 


222  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Variety. — Pickled  Mission,  Manzanillo,  Sevillano,  and  Ascolano, 
from  a  single  factory,  were  canned  and  sterilized  at  240°  F.  for  40 
minutes.  Several -lots  of  Mission  and  Manzanillo  olives  were  pickled 
in  the  laboratory  and  were  sterilized  in  the  same  way.  The  flavor  and 
texture  of  the  different  varieties  were  compared  immediately  after  can- 
ning, one  month  later,  and  six  months  later.  Numerous  samples  of 
Mission,  Manzanillo,  and  Sevillano  olives  canned  on  a  commercial  scale 
and  sterilized  at  240°  F.  for  40  minutes  have  also  been  examined  and 
compared. 

As  a  result  of  these  comparisons,  it  was  found  that  the  Manzanillo 
variety  was  more  sensitive  to  high  temperatures  than  any  of  the  other 
varieties  named.  The  Sevillano  variety  was  remarkably  resistant  and 
in  many  instances  was  improved  in  flavor  by  sterilization  at  240°  F. 
The  Mission  variety,  when  properly  pickled,  suffered  very  little  in 
quality  from  the  high  temperature.  All  varieties,  however,  varied 
greatly  in  their  behavior  according  to  the  treatment  given  before 
canning. 

Maturity. — Manzanillo  olives  deteriorated  in  flavor  and  texture  at 
240°  F.  very  much  more  when  perfectly  ripe  than  when  unripe. 
Mission  olives  showed  less  difference  in  this  respect. 

No  data  were  obtained  on  the  effect  of  maturity  of  Ascolano  and 
Mission  olives  on  their  behavior  at  high  temperatures.  These  varie- 
ties are  normally  gathered  for  pickling  before  they  are  fully  mature. 

Holding  Solutions. — Olives  are  often  held  in  brine  or  water  for 
several  weeks  before  they  are  pickled.  They  are  usually  shipped 
in  barrels  or  tank  cars,  in  dilute  brine,  from  the  orchard  to  the  factory. 
Laboratory  experiments  and  factory  observations  have  proved  that 
olives  stored  in  water  frequently  become  slimy  and  undergo  bacterial 
decomposition.  Microscopic  examination  of  olives  stored  in  water  for 
about  three  weeks  in  three  factories  demonstrated  the  presence  of  mold 
filaments  and  motile  bacteria  in  the  olive  flesh  and  a  slimy  growth 
of  mold  and  yeastlike  organisms  on  the  surface  of  the  fruit.  Some 
of  the  fruit  in  these  three  lots  had  undergone  visible  decomposition. 
Unless  the  storage  in  water  is  for  a  short  period  only  (a  week  or  less) 
or  the  water  is  changed  frequently,  the  use  of  water  for  the  storage 
of  olives  is  not  advisable. 

In  practically  all  factories,  brines  are  now  used  as  holding  solu- 
tions. There  is  great  variation,  however,  in  the  strength  of  these 
brines.  Analyses  have  shown  concentrations  varying  from  1.2  per  cent 
to  10  per  cent  salt,  the  average  being  approximately  3  per  cent.  The 
density  of  these  solutions  averaged  approximately  1°  Baume  above 
the  percentage  of  the  salt  determined  by  chemical  analysis.    The  olives 


Bulletin  333]  0LIVE  CANNING  223 

in  a  10  per  cent  brine  (40°  salometer  test)  gave  no  evidence  of  mold 
growth  or  of  fermentation.  Those  in  very  dilute  brines  in  some 
instances  exhibited  vigorous  mold  growth,  active  fermentation,  and 
some  softening  of  the  flesh.  Although  fermentation  and  formation 
of  acid  occurred  in  olives  in  brines  of  4  to  6  per  cent  salt  (16  to  24° 
salometer),  the  olives  did  not  have  a  disagreeable  odor  and  had  become 
considerably  firmer  than  when  first  placed  in  the  brine.  It  is  probable 
that  the  lactic  acid  formed  in  such  brines  retards  the  growth  of 
undesirable  organisms,  such  as  Bacillus  botulinus,  but  the  use  of  a 
brine  of  10  per  cent  salt  (40°  salometer)  is  undoubtedly  more  effective. 
If  very  strong  brines  are  used,  it  is  necessary  to  increase  the  salt 
concentration  gradually  and  progressively  in  order  to  avoid  shrivelling 
of  the  fruit.  On  this  account,  it  is  not  convenient  to  use  a  10  per  cent 
brine  for  shipping  unpickled  olives.  A  5  per  cent  brine  may  be  used 
for  this  purpose,  however,  and  more  salt  may  be  added  after  the  arrival 
of  the  fruit  at  the  factory.  The  brine  should  be  leached  from  the 
fruit  by  soaking  the  fruit  in  water  before  it  is  pickled. 

Experiments  and  experience  have  proved  that  storage  of  soft  and 
over-ripe  olives  in  brine  makes  them  firmer  and  of  more  uniform 
quality  after  pickling.  Whether  prime  ripe,  sound,  and  firm  olives 
are  improved  by  storage  in  brine  before  pickling  is  an  open  question. 

Lye  Treatment. — In  order  to  determine  the  relation  of  the 
thoroughness  of  the  lye  treatment  to  the  flavor  and  texture  of  olives 
sterilized  at  240°  F.,  a  number  of  samples  representing  different  pick- 
ling processes  and  the  different  stages  of  the  pickling  process  were 
canned  and  sterilized  at  240°  F.  for  40  minutes.  Some  of  these 
samples  were  canned  in  commercial  olive  packing  plants  and  others 
were  pickled  and  canned  in  the  laboratory.  The  experiments  are 
summarized  in  the  following  list. 

List  of  Experiments  Conducted  to  Determine  the  Kelation  of  Lye  Treatment 
to  Quality  of  Olives  Sterilized  at  240°  F.  for  40  Minutes 

Character  of  sample  Result 

1."  Unpickled     olives     direct     from     tree     Badly  softened. 
(Mission,      Manzanillo,      Sevillano, 
Ascolano  varieties). 

2.  Unpickled   Mission    olives   after   three     About   75   per  cent   of  fruit  softened. 

weeks  in  holding  brine.  Eemainder  firm. 

3.  Mission  and  Manzanillo  olives  contain-     Very  pronounced  scorched  flavor.  About 

ing  small  excess  of  lye  from  final         25  per  cent  of  fruit  badly  softened. 

lye  treatment.   Five  samples  of  each 

variety. 


224 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Character  of  sample 

4.  Mission,     Manzanillo,     and     Sevillano 

olives  pickled  and  sorted  out  as 
"bitters"  at  cannery  table.  Con- 
tained considerable  bitter  flesh  at 
blossom  end  of  fruit.  Several  sam- 
ples of  each  variety. 

5.  Pickled    Manzanillo    olives    containing 

considerable  bitterness.  These  came 
from  a  factory  that  canned  olives 
with  this  degree  of  bitterness. 

6.  Olives  of  same  lot  as  No.  5  treated  in 

laboratory  with  1  per  cent  lye  to 
pit.  Canned  after  removal  of  lye 
by  leaching. 

7.  Slightly  bitter  pickled  Mission   olives 

from  three  factories,  canned  in 
laboratory.  Eepresentative  of  usual 
pack  of  these  factories. 

8.  Same  as  No.  7,  but  treated  to  pit  with 

1  per  cent  lye.  Lye  leached  from 
fruit  with  water  before  canning. 


Result 
Pronounced      scorced      flavor.        From 
25-75    per    cent    of    fruit    soft    and 
"mushy"  at  blossom  end. 


Pronounced    scorced   flavor    and    10-25 
per  cent  of  fruit  badly  softened. 


No  softening.  Very  faint  scorched 
flavor.  Color  somewhat  lighter  than 
sample  No.   5  but  still  satisfactory. 

Pronounced  bitter  almond  odor  and 
scorched  flavor.  Five  to  10  per  cent 
of  fruit  softened  at  blossom  end  of 
fruit. 

No  bitter  almond  odor  or  scorched 
flavor.  No  softening.  Color  not 
quite  so  dark  as  in  No.  7. 


From  these  experiments  it  was  concluded  that  the  development 
of  scorched  flavor,  bitter  almond  odor,  and  excessive  softening  of  the 
fruit  observed  in  several  factories  during  sterilization  was  due,  at 
least  in  part,  to  insufficient  lye  treatment  or  to  the  presence  in  the 
fruit  of  excess  lye.  The  experiments  proved  that  slightly  bitter 
pickled  olives  can  be  treated  with  a  dilute  lye  solution  to  remove  all 
trace  of  bitterness,  and  be  canned  with  good  results  after  the  lye  has 
been  removed  by  leaching  with  water.  Too  prolonged  treatment  or 
too  strong  lye  results  in  softening  and  loss  of  color. 

A  convenient  method  of  detecting  very  bitter  olives  in  more  per- 
fectly pickled  fruit  consisted  in  heating  the  olives  in  brine  and  boiling 
for  about  twenty  minutes.  Very  bitter  fruit  softened  and  could  then 
be  easily  detected  and  removed  at  the  sorting  tables.  It  is  possible, 
however,  to  treat  the  olives  so  thoroughly  with  lye  that  no  bitter  fruit 
will  be  found. 

Bacterial  Action. — Fruit  softened,  injured  in  flavor,  or  otherwise 
damaged  by  bacterial  growth  in  the  fruit  before  pickling,  was  not 
improved  by  sterilization  at  240°  F.  Unpickled  fruit  which  had  been 
fermented  in  holding  solutions  without  softening,  remained  firm  after 
sterilization. 


Bulletin  333]  OLIVE  CANNING  225 

Excessive  bacterial  growth  in  the  fruit  during  pickling  and  during 
the  following  storage  in  brine  resulted  in  softening  of  a  large  propor- 
tion and  in  injury  to  the  flavor.  Fermentation  of  the  pickled  fruit 
before  canning  caused  the  color  to  become  lighter  and  formed  "gas 
pockets"  in  the  flesh  which  collapsed  during  sterilization,  giving  a 
pitted  appearance  to  the  fruit. 

By  the  use  of  holding  solutions  of  sufficient  strength  for  fresh  fruit 
and  by  not  permitting  the  pickled  olives  to  remain  too  long  in  dilute 
brine  before  canning,  the  above  defects  may  be  avoided. 

Salt  Concentration. — Increase  of  the  strength  of  the  brine  used  in 
canning  reduced  the  tendency  of  the  olives  to  soften,  but  the  use  of 
concentrations  above  4  per  cent  salt  (16°  salometer)  rendered  the  fruit 
too  salty  in  flavor.  Better  results  were  obtained  by  placing  the  pickled 
fruit  in  a  brine  of  8  per  cent  to  9  per  cent  (32°-36°  salometer)  for 
four  to  six  days  and  canning  the  fruit  in  water.  Although  shrivelled 
in  appearance  and  very  salty  in  flavor  at  the  time  of  canning,  the 
olives  became  plump  and  not  too  salty  in  flavor  after  canning. 

Gradual  increase  of  the  brine  from  6  per  cent  to  7  per  cent  (24°  to 
28°  salometer)  after  pickling,  followed  by  canning  in  a  2y2  to  2  per 
cent  brine  (8°  to  10°  salometer),  caused  the  olives  to  be  firmer  than 
if  canned  directly  from  the  storage  in  2y2  or  3  per  cent  brine. 

As  olives  decrease  in  size  when  stored  in  strong  brines  and  in- 
crease in  size  when  transferred  to  water  or  dilute  brine,  less  fruit 
than  would  otherwise  be  necessary  is  required  to  give  a  well  filled  can. 

Increase  of  Acidity  of  Brine. — It  has  been  proved  by  Dr.  E.  C. 
Dickson,1  of  Stanford,  by  the  writer,2  and  more  recently  confirmed 
by  Weiss,3  that  the  spores  of  heat-resistant  bacteria  are  more  easily 
killed  by  heat  in  an  acid  solution  than  in  a  neutral  one.  Pickled  ripe 
olives  and  the  brine  in  which  they  are  canned  are  practically  neutral. 

During  both  the  1919  and  1920  seasons,  ripe  pickled  olives  of  the 
Mission  and  Manzanillo  varieties  were  stored  in  brines  acidified  to 
various  degrees  with  citric,  acetic,  and  lactic  acids  respectively.  These 
olives  were  in  some  instances  canned  in  the  brine  in  which  they  were 
stored  and  in  others  in  freshly  prepared  non-acidified  brines.  Some 
cans  were  sterilized  at  240°  F.  for  40  minutes  and  others  at  212°  F. 
for  60  minutes. 


1  E.    C.    Dickson.      Botulism.      Eeprint    from    the    Canadian    Medical    Journal. 
October,  1918,  p.  5. 

2  W.  V.  Cruess.     Home  Canning-  of  Fruits  and  Vegetables.     Circular  158,  Uni- 
versity of  California  Experiment  Station,  1915,  p.  4. 

s  H.  Weiss.     ' '  The  Heat  Eesistance  of   Spores  with   Special  Eef erence  to  B. 
botulinus. "     Journal  of  Infectious  Diseases,  1921,  pp.  70-92. 


226  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Formation  of  hydrogen  gas  and  swelling  of  the  cans  occurred  with 
citric  acid  when  the  acidity  of  the  brine  in  which  the  olives  were 
soaked  exceeded  .3  per  cent.  Brines  of  .25  per  cent  or  less  did  not 
cause  swelling  of  the  cans.  The  formation  of  the  gas  resulted  from 
the  action  of  the  acid  on  the  tin  plate.  There  was  no  evidence  of 
bacterial  growth  in  any  of  the  samples  canned  (approximately  300 
cans). 

The  acidity  of  the  brine  was  much  less  after  canning  than  when 
placed  upon  the  olives.  This  reduction  in  acidity  was  probably  due 
in  part  to  absorption  of  acid  by  the  fruit  and  in  part  to  neutraliza- 
tion of  a  part  of  the  acid  by  basic  salts  in  the  fruit.  Brines  which 
originally  contained  .3  per  cent  citric  acid  contained  from  .1  per  cent 
to  .14  per  cent  after  canning. 

The  olives  soaked  in  brine  of  .3  per  cent  citric  acid  were  decidedly 
"tart"  in  flavor,  very  much  toughened  in  texture,  and  considerably 
bleached  in  color.  They  were  not  of  satisfactory  quality.  Brines  of 
.2  per  cent  citric  acid  gave  a  product  of  pleasing  flavor,  but  of  some- 
what lighter  color  and  of  tougher  texture  than  the  untreated  samples. 

Acetic  acid  imparted  a  disagreeable  odor  and  flavor  to  the  olives. 
Lactic  acid  gave  results  similar  to  citric  acid. 

Acidification  of  the  brines  is  not  recommended,  because  it  causes 
more  serious  changes  in  the  quality  of  the  fruit  than  occur  through 
sterilization  of  the  non-acidified  pickled  fruit  at  240°  F.  for  40  minutes. 

Temperature. — Olives  of  the  Mission,  Manzanillo,  and  Sevillano 
varieties  were  canned  experimentally  and  heated  to  temperatures 
ranging  from  190°  F.  to  250°  F.,  and  for  lengths  of  time  varying 
from  15  to  60  minutes  at  the  higher  temperatures  and  from  20  to 
120  minutes  at  212°  F.  Numerous  samples  of  these  varieties  canned 
commercially  in  1919  and  1920  in  olive  factories,  were  also  compared. 
These  commercial  samples  represented  processing  temperatures  of 
190°  F.  to  250°  F. 

In  one  test,  Mission  olives  of  large  size,  black  color,  and  free  from 
bitterness,  were  canned  and  heated  as  follows : 

212°  F.,  45,  and  120  minutes. 

220°  F.,  15,  30,  and  60  minutes. 

225°  F.,  15,  30,  and  60  minutes. 

230°  F.,  15,  30,  40,  and  60  minutes. 

235°  F.,  15,  30,  40,  and  60  minutes. 

240°  F.,  15,  30,  40,  and  60  minutes. 

250°  F.,  15,  30,  40,  and  60  minutes. 

The  olives  were  canned  in  six-ounce  plain  tin  cans  and  were  not 
cooled  in  water  after  heating. 


Bulletin  333] 


OLIVE  CANNING 


227 


About  10  per  cent  of  the  fruit  softened  excessively  when  heated 
to  250°  F.  for  40  and  60  minutes,  and  to  240°  F.  for  60  minutes.  A 
sample  heated  to  260°  F.  for  60  minutes  was  still  edible,  but  badly 
softened.    The  olives  heated  to  250°  F.  for  15,  30,  40,  and  60  minutes 


Fig.  1. — Upper  view:  Large  horizontal  steam  pressure  retort  with  recording 
thermometer.  Used  for  olive  sterilization.  Lower  view:  Small  steam  pressure 
retort  suitable  for  the  small  scale  olive  canner. 


and  to  240°  F.  for  30,  40,  and  60  minutes  had  a  marked  scorched 
flavor.  Those  heated  to  240°  F.  for  15  minutes,  235  F.  for  40  and 
60  minutes,  and  to  220°  F.  for  60  minutes  were  of  noticeable  but  not 
marked  scorched  flavor.     The  scorched  flavor  was  not  evident  in  other 


228  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

samples  of  this  series.  After  one  month 's  storage,  the  scorched  flavor 
had  very  greatly  diminished  in  all  samples.  After  six  months'  storage, 
most  of  the  scorched  flavor  had  disappeared.  The  samples  were  again 
examined  at  the  end  of  eighteen  months,  and  it  was  found  that  the 
fruit  heated  to  250°  F.  and  240°  F.  had  still  further  improved  in 
flavor.  The  olives  sterilized  at  250°  F.  and  240°  F.  for  40  and  60 
minutes  were  lighter  in  color  immediately  after  heating  than  those 
less  severely  heated.  After  six  and  eighteen  months '  storage,  respec- 
tively, there  was  very  little  difference  in  color ;  but  the  olives  heated 
to  250°  F.  and  to  240°  F.  were  in  most  samples  a  little  darker  than 
those  heated  to  212°  F. 

As  stated  elsewhere  in  this  publication  (see  Lye  Treatment,  page 
223),  the  presence  in  the  olives  of  flesh  which  had  not  been  penetrated 
by  lye,  resulted  in  the  development  at  240°  F.  of  a  very  pronounced 
scorched  flavor,  and  in  softening  of  the  fruit.  This  was  true  par- 
ticularly of  the  Manzanillo  variety.  Many  of  the  commercially  canned 
olives  sterilized  at  240°  F.  for  40  minutes  during  the  1920  season 
appeared  to  be  badly  damaged  in  flavor.  However,  at  the  present 
time  (July,  1921)  this  fruit  has  "recovered"  in  flavor  and  is,  on 
the  average,  of  very  good  quality.  The  Sevillano  variety  has  suffered 
least  and  the  Manzanillo  most  b}^  sterilization  at  240°  F.  in  the  fac- 
tories in  the  state.  The  Mission  variety  occupies  an  intermediate 
position. 

That  properly  pickled  olives  sterilized  at  240°  F.  for  40  minutes 
are  acceptable  to  the  average  consumer  has  been  demonstrated  on  a 
number  of  occasions  by  asking  classes  of  students  and  other  groups 
of  people  to  compare  the  flavor  of  olives  heated  in  this  manner  with 
those  heated  to  212°  F.  In  many  instances,  the  olives  sterilized  at 
240°  F.  were  preferred,  because  of  their  more  distinctive  flavor. 

It  is  therefore  permissible  to  conclude  that  pickled  ripe  olives  may 
be  sterilized  at  240°  F.  for  40  minutes,  according  to  the  regulation 
of  the  State  Board  of  Health,  without  serious  damage  to  the  quality 
of  the  product. 

Rapid  chilling  of  the  can  and  contents  to  room  temperature 
immediately  after  sterilizing  is  desirable  in  order  to  prevent  pro- 
longed action  of  the  heat. 

Investigations  in  1919  by  De  Bord,  Edmonson,  and  Thorn,  of  the 
lT.  S.  Department  of  Agriculture,4  indicated  that  many  canned  olives 
on  the  market  at  that  time  were  not  sterile ;  but,  in  the  investigations 
reported,  no  data  are  given  on  the  relation  between  sterility  and  the 

*  G.  G.  Do  Bord,  R.  B.  Edmonson,  C.  Thorn,  Journal  American  Medical  Asso- 
ciation, vol.  74,  pp.  1220-1221   (May  1,  1920). 


Bulletin  333] 


OLIVE  CANNING 


229 


temperature  employed  in  canning.  H.  K.  Beresford5  found  that 
nearly  all  samples  heated  to  190°  F.  and  212°  F.  examined  by  him 
were  not  sterile;  that  of  those  heated  to  220,  225,  and  230°  F.  for 
20  to  30  minutes,  about  15  per  cent  were  not  sterile,  and  of  those 
heated  to  240°  F.  for  30  minutes,  and  to  250°  F.  for  15  minutes,  all 
were  sterile.  The  experiments  were  not  sufficiently  extensive  to  be 
conclusive,  but  the  results  are  of  sufficient  interest  to  warrant  pub- 
lication. 


Fig.  2. — Pickling  vats  in  a  California  factory. 

Character  of  Container. — Olives  canned  in  1915  in  enameled  lined 
cans  had  retained  their  color  much  more  satisfactorily,  after  one  year's 
storage,  than  olives  from  the  same  lot  in  plain  tin  cans.  The  brine 
was  clearer  but  darker  in  color  in  the  lacquered  cans.  No  difference 
was  noted  in  flavor.  Several  of  the  cans  of  both  kinds  were  recently 
opened  (six  years  after  canning)  and  the  differences  noted  above  had 
become  even  more  striking. 

The  experiments  were  repeated  in  1920  with  six  lots  of  olives 
representing  both  Mission  and  Manzanillo.  Six  months  after  steril- 
ization at  240°  F.  for  40  minutes,  the  olives  in  lacquered  cans  were 
noticeably  darker  in  color  than  those  in  tin  cans.  Apparently,  the 
action  of  the  brine  or  of  fruit  compounds  upon  the  tin  plate  results 
in  the  formation  of  sufficient  hydrogen  to  cause  bleaching  of  the 
olives.  The  bleaching  action  is  temporary,  as  is  proved  by  the  fact 
that  the  olives  from  the  plain  tin  cans  regained  much  of  their  original 
color  when  exposed  to  the  air  for  24  hours. 

5  Formerly  a  student  in  the  University. 


230  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Olives  in  glass  jars  sterilized  at  240°  F.  for  40  minutes  developed 
a  pitted  appearance  when  the  jars  were  opened  later.  This  may  pos- 
sibly be  explained  as  follows:  The  caps  of  these  jars  do  not  prevent 
the  escape  of  gases  or  steam  under  heavy  pressure.  Consequently,  as, 
after  the  steam  pressure  in  the  sterilizer  is  cut  off,  the  jars  and  olives 
remain  for  a  short  time  at  a  temperature  above  that  of  the  space  in 
the  sterilizer  surrounding  the  jars,  steam  is  formed  in  the  jars  and 
escapes  between  the  jar  and  the  cap,  which  acts  as  a  valve.  Steam  is 
probably  generated  violently  in  the  olive  flesh  and  ruptures  it,  form- 
ing "pockets."  These  "pockets"  are  plainly  visible  when  such  olives 
are  cut  to  the  pit.  As  the  jars  cool,  the  caps  become  cemented  to  the 
glass  and  form  an  air-tight  seal.  As  cooling  continues,  a  vacuum  is 
formed  in  the  jar  and  under  its  action,  the  olives  become  plump  in 
spite  of  the  presence  of  the  "pockets"  in  their  flesh.  When  such  a 
jar  is  opened,  however,  the  vacuum  is  released  and  the  fruit  is  sub- 
jected to  atmospheric  pressure  which  causes  depressions  where  the 
"pockets"  exist.  Olives  sterilized  at  240°  F.  in  open  cans,  or  cans 
in  the  tops  of  which  small  holes  are  made,  develop  the  pitted  appear- 
ance noted  above.  Those  in  perfectly  sealed  cans  do  not  exhibit  this 
phenomenon. 

The  use  of  air  under  high  pressure  with  the  steam  in  the  steril- 
ization of  olives  in  glass  jars  has  overcome  the  difficulty  in  one  factory, 
although  rapid  circulation  of  the  air  and  steam  in  the  retort  is  neces- 
sary to  insure  a  uniform  temperature  throughout.  Circulation  is 
attained  by  use  of  open  petcocks  on  the  retort. 

Gallon  cans  and  cans  of  other  large  sizes  frequently  become 
"buckled"  or  in  some  instances  open  at  the  top  and  bottom  seams 
unless  cooled  under  air  pressure  in  the  retorts.  The  tendency  to 
"buckle"  was  greatly  reduced  when  the  cans  and  olives  were  thor- 
oughly heated  in  the  exhaust  box  to  195°  F.  before  sealing. 


Bulletin  333]  OLIVE  CANNING  231 


SUMMARY  AND  CONCLUSIONS 

1.  Properly  pickled  olives  yield  an  acceptable  product  when  ster- 
ilized at  240°  F.  for  40  minutes. 

2.  The  Manzanillo  olive  is  more  subject  to  damage  in  flavor  and 
texture  at  240°  F.  than  the  Mission,  Sevillano,  and  Ascolano  varieties. 

3.  Very  ripe  olives  are  more  liable  to  damage  at  240°  F.  than  less 
mature  fruit,  Manzanillo  olives,  particularly,  should  not  be  too  ripe 
when  pickled. 

4.  Brines  of  sufficient  strength  to  prevent  decomposition  of  the 
olives  should  be  used  for  holding  solutions.  Brine  of  5  per  cent  salt 
(20°  salometer)  is  recommended  for  shipment  of  olives,  and  one  of 
10  per  cent  salt  (40°  salometer)  for  holding  olives  in  the  factory  for 
long  periods. 

5.  Lye  treatment  must  be  thorough  and  all  bitterness  removed  if 
the  best  flavor  and  texture  are  to  be  obtained  in,  olives  sterilized  at 
240°  F. 

6.  Fermentation  and  bacterial  action  in  the  pickled  fruit  causes 
"floaters"  and  pitting  of  the  fruit.  Long  storage  of  pickled  fruit 
in  dilute  brine  should  therefore  be  avoided. 

7.  Storage  of  the  fruit  in  strong  brine  for  several  days  followed 
by  canning  in  very  dilute  brine  or  water  makes  the  texture  of  the 
fruit  firmer. 

8.  Acidified  brines  act  vigorously  upon  the  tin  plate  and  impart 
an  undesirable  flavor  to  the  fruit. 

9.  Olives  retain  their  color  more  satisfactorily  in  lacquered  than 
in  plain  cans. 

10.  The  scorched  flavor  noted  in  most  olives  immediately  after 
sterilization  at  240°  F.  rapidly  diminishes  during  storage. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 

BULLETINS 


No. 
185. 

231. 

241. 
246. 
251. 

253. 

261. 
262. 

263. 
266. 

267. 
268. 
270. 


271. 
272. 
273. 

274. 

275. 

276. 

278. 
279. 
280. 

282. 

283. 
285. 
286. 
288. 

290. 

294. 


Report  of  Progress  in  Cereal  Investiga- 
tions. 

Walnut  Culture  in  California. 

Vine  Pruning  in  California,  Part  I. 

Vine  Pruning  in  California,  Part  II. 

Utilization  of  the  Nitrogen  and  Organic 
Matter  in  Septic  and  Imhoff  Tank 
Sludges. 

Irrigation  and  Soil  Conditions  in  the 
Sierra  Nevada  Foothills,  California. 

Melaxuma  of  the  Walnut,  "Juglans  regia." 

Citrus  Diseases  of  Florida  and  Cuba 
Compared  with  Those  of  California. 

Size  Grades  for  Ripe  Olives. 

A  Spotting  of  Citrus  Fruits  Due  to  the 
Action  of  Oil  Liberated  from  the  Rind. 

Experiments  with  Stocks  for  Citrus. 

Growing  and  Grafting  Olive  Seedlings. 

A  Comparison  of  Annual  Cropping,  Bi- 
ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

Feeding  Dairv  Calves  in  California. 

Commercial  Fertilizers. 

Preliminary  Report  on  Kearney  Vineyard 
Experimental  Drain. 

The  Common  Honey  Bee  as  an  Agent  in 
Prune  Pollination. 

The  Cultivation  of  Belladonna  in  Cali- 
fornia. 

The  Pomegranate. 

Grain  Sorghums. 

Irrigation  of  Rice  in  California. 

Irrigation  of  Alfalfa  in  the  Sacramento 
Valley. 

Trials  with   California   Silage   Crops   for 

•  Dairv  Cows. 

The  Olive  Insects  of  California. 

The  Milk  Goat  in  California. 

Commercial  Fertilizers. 

Potash  from  Tule  and  the  Fertilizer  Value 
of  Certain  Marsh  Plants. 

The  June  Drop  of  Washington  Navel 
Oranges. 

Bean  Culture  in  California. 


No. 

297.  The  Almond  in  California. 

298.  Seedless  Raisin  Grapes. 

299.  The  Use  of  Lumber  on  California  Farms. 

300.  Commercial  Fertilizers. 

301.  California  State  Dairy  Cow  Competition, 

1916-1918. 

302.  Control  of  Ground  Squirrels  by  the  Fumi- 

gation Method. 

303.  Grape  Syrup. 

304.  A    Study   on   the   Effects    of   Freezes  on 

Citrus  in  California. 

308.  I.  Fumigation  with   Liquid  Hydrocyanic 

Acid.    II.  Physical  and  Chemical  Pro- 
perties of  Liquid  Hydrocyanic  Acid. 

309.  I.  The  Carob  in  California.    II.  Nutritive 

Value  of  the  Carob  Bean. 

310.  Plum  Pollination. 

311.  Investigations  with  Milking  Machines. 

312.  Mariout  Barley. 

313.  Pruning  Young  Deciduous  Fruit  Trees. 

316.  The  Kaki  or  Oriental  Persimmon. 

317.  Selections  of  Stocks  in  Citrus  Propagation. 

318.  The  Effects  of  Alkali  on  Citrus  Trees. 

319.  Caprifigs  and  Caprification. 

320.  Control  of  the  Coyote  in  California. 

321.  Commercial  Production  of  Grape  Syrup. 

322.  The  Evaporation  of  Grapes. 

323.  Heavy  vs.  Light  Grain  Feeding  for  Dairy 

Cows. 

324.  Storage   of  Perishable  Fruit  at  Freezing 

Temperatures. 

325.  Rice    Irrigation    Measurements   and    Ex- 

periments in  Sacramento  Valley,  1914- 
1919. 

326.  Brown  Rot  of  Apricots. 

327.  Commercial  Fertilizers. 

328.  Prune  Growing  in  California. 

329.  A  White  Fir  Volume  Table. 

330.  Dehydration  of  Fruits. 

331.  Phylloxera-Resistant  Stocks. 

332.  Walnut  Culture  in  California. 

333.  Some    Factors    Affecting   the   Quality    of 

Ripe    Olives    Sterilized   at    High    Tem- 
peratures. 


CIRCULARS 


No.  No. 

70.  Observations    on    the    Status    of    Corn  154. 

Growing  in  California. 

76.  Hot  Room  Callusing.  155. 

82.  The  Common  Ground  Squirrels  of  Cali-  157. 

fornia.  158. 

87.  Alfalfa.                          '  159. 

110.  Green  Manuring  in  California.  160. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali-  161. 

fornia  Soils.  164. 

113.  Correspondence  Courses  in  Agriculture.  165. 

114.  Increasing  the  Duty  of  Water. 

115.  Grafting  Vinifera  Vineyards.  166. 
117.  The  Selection  and  Cost  of  a  Small  Pump-  167. 

ing  Plant.  168. 

126.  Spraying  for  the  Grape  Leaf  Hopper. 

127.  House  Fumigation.  169. 

128.  Insecticide  Formulas.  170. 

129.  The  Control  of  Citrus  Insects. 

130.  Cabbage  Growing  in  California.  172. 

131.  Spraying  for  Control  of  Walnut  Aphis.  173. 
135.  Official  Tests  of  Dairy  Cows.  174. 

137.  Wood  Decay  in  Orchard  Trees.  175. 

138.  The  Silo  in  California  Agriculture. 

139.  The  Generation  of  Hydrocyanic  Acid  Gas  176. 

in  Fumigation  by  Portable  Machines. 

144.  Oidium  or  Powdery  Mildew  of  the  Vine.  177. 

148.  "Lungworms."  178. 

151.  Feeding  and  Management  of  Hogs.  179. 

152.  Some  Observations  on  the  Bulk  Handling 

of  Grain  in  California.  181. 

153.  Announcement    of    the    California    State  182. 

Dairy  Cow  Competition,  1916-18. 


Irrigation    Practice    in    Growing    Small 

Fruits  in  California. 
Bovine  Tuberculosis. 
Control  of  the  Pear  Scab. 
Home  and  Farm  Canning. 
Agriculture  in  the  Imperial  Valley. 
Lettuce  Growing  in  California. 
Potatoes  in  California. 
Small  Fruit  Culture  in  California. 
Fundamentals    of    Sugar    Beet    Culture 

under  California  Conditions. 
The  County  Farm  Bureau. 
Feeding  Stuffs  of  Minor  Importance. 
Spraying  for  the  Control  of  Wild  Morning- 
Glory  within  the  Fog  Belt. 
The  1918  Grain  Crop. 
Fertilizing  California  Soils  for  the   1918 

Crop. 
Wheat  Culture. 

The  Construction  of  the  Wood-Hoop  Silo. 
Farm  Drainage  Methods. 
Progress  Report  on  the   Marketing  and 

Distribution  of  Milk. 
Hog  Cholera  Prevention  and  the  Serum 

Treatment. 
Grain  Sorghums. 

The  Packing  of  Apples  in  California. 
Factors  of  Importance  in  Producing  Milk 

of  Low  Bacterial  Count. 
Control  of  the  California  Ground  Squirrel. 
Extending  the  Area  of  Irrigated  Wheat  in 

California  for  1918. 


CIRCULARS— Continued 


No. 
183. 
184. 
185. 


Infectious  Abortion  in  Cows. 
A  Flock  of  Sheep  on  the  Farm. 
Beekeeping  for  the  Fruit-grower  and  Small 

Rancher  or  Amateur. 
Lambing  Sheds. 

189.  Winter  Forage  Crops. 

190.  Agriculture  Clubs  in  California. 

191.  Pruning  the  Seedless  Grapes. 

193.  A  Study  of  Farm  Labor  in  California. 
198.  Syrup  from  Sweet  Sorghum. 

Helpful  Hints  to  Hog  Raisers. 

County  Organizations  for  Rural  Fire  Con- 
trol. 

Peat  as  a  Manure  Substitute. 

204.  Handbook    of   Plant    Diseases   and   Pest 

Control. 

205.  Blackleg. 

206.  Jack  Cheese. 

208.  Summary  of  the  Annual  Reports  of  the 

Farm  Advisors  of  California. 

209.  The  Function  of  the  Farm  Bureau. 


188. 


201. 

202. 


203. 


No. 

210.  Suggestions  to  the  Settler  in  California. 

214.  Seed    Treatment    for    the   Prevention    of 

Cereal  Smuts. 

215.  Feeding  Dairy  Cows  in  California. 

217.  Methods    for    Marketing    Vegetables    in 

California. 

218.  Advanced  Registry  Testing  of  Dairy  Cows. 

219.  The  Present  Status  of  Alkali. 
220. 
221. 


Unfermented  Fruit  Juices. 

How  California  is  Helping  People  Own 

Farms  and  Rural  Homes. 
Fundamental   Principles  of   Co-operation 

in  Agriculture. 
The  Pear  Thrips. 
224.  Control  of  the  Brown  Apricot  Scale  and 

the    Italian   Pear    Scale    on    Deciduous 

Fruit  Trees. 
Propagation  of  Vines. 

Protection  of  Vineyards  from  Phylloxera. 
Plant  Disease  and  Pest  Control. 


222. 
223. 


225. 
223. 

227. 


